The present invention is directed to improvements in filters and in particular to rotary vacuum disc filters.
Vacuum disc filters are well known and comprise banks of filter discs mounted in spaced side by side relationship on a rotatable center shaft assembly arranged within a slurry tank. Each filter disc is comprised of a plurality of V-shaped filter sectors with the filter sections of one disc aligned with the filter sectors of the adjacent discs on the center shaft. A plurality of filtrate flow channels are located in the center shaft assembly with each flow channel adapted to receive the filtrate from one row of aligned filter sectors. Each filter sector is usually provided with an outer filter media such as a filtrate bag or the like and is detachably connected to the center shaft assembly and a flow channel by means of an appropriate drainage connection.
In use the filter shaft assembly rotates the discs through the slurry in the tank and a vacuum is applied to the center shaft to draw filtrate through the filter sectors and outwardly of the filter through the filtrate channels as filter cake adheres to the surface of the filter media. At a preselected point in the filter cycle as the discs rotate out of the slurry tank the vacuum is cut off from a portion of the discs and an appropriate doctor means or snap blow means is applied to remove the filter cake from that portion of the discs prior to reentry thereof into the slurry tank.
These type vacuum disc filters have met with wide acceptance and are used in many industries. Problems have been encountered, however, in instances where damage is caused to the filter media and its associated filter sector as a result of abrasive material in the slurry. In these instances the non-filtered slurry is apt to be drawn into the filter sector and its associated filtrate channel which often results in damage thereto and contamination of the filtrate discharging from the remaining filtrate channels. It has been common practice therefore where a filter sector is damaged to discontinue operation of the filter until time is permitted for replacement of the sector itself. The latter stoppage resulted in production delays and high labor costs of operation.
It is an object of the present invention to provide a vacuum disc filter having novel means for selectively stopping the filtrate flow in a selected filtrate channel of a filter disc assembly.
Another object is to provide novel means for selectively stopping the flow of filtrate in a selected filtrate channel of a center shaft assembly of a vacuum type disc filter without causing material delay in operation of the filter.